JP3515972B2 - Projection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection device such as a projection type projector for forming an image by an electronic member and its optical system.

[0002]

2. Description of the Related Art Projection devices such as projection type projectors are widely used for cinema screening in movie theaters and for presentations at academic conferences and sales activities. However, there is a continuing demand for higher resolution and higher image quality, as well as for compactness for convenience in portable and reduction of occupied area.

At present, as a basic specification of a liquid crystal projector, for cinema screening, generally, three color liquid crystal panels for three primary colors or a digital micromirror device, that is, DMD for three primary colors is used without using a color wheel. (Digital Micro mirror Device) is used as a display panel. On the other hand, for business and low-cost models, a color wheel and three liquid crystal panels for three primary colors are used, or a single-panel liquid crystal panel for three primary colors or a single-plate digital micromirror device for three primary colors is used. You can see many things you did.

Digital micromirror devices are
Since the illumination optical system can be simply configured, the projection device can be downsized, and the cooling efficiency is excellent, the number of models equipped with this is increasing. Furthermore, since the digital micromirror device can have a high aperture ratio, it can easily achieve high brightness and can also have high reliability.

Furthermore, a digital micromirror
The device has a very high response speed in each pixel unit, and does not need to have a three-layer structure unlike a transmissive liquid crystal panel. This is because it is possible to perform a digital image expression using the optical illusion by rotating the color conversion filters at high speed sequentially using a color wheel or the like.

As a projection apparatus using a digital micromirror device, as shown in FIG. 9, a light valve 112 with a reflector 110 and a projection optical axis O of the reflector 110 are provided in a housing (not shown). Color wheel 114 and light pipe 11 arranged orthogonally
6, a condenser lens 121, a first mirror 118 that is an obliquely arranged flat surface mirror, and a reflection optical axis O of the first mirror 118
A second mirror 120 of a concave surface mirror obliquely installed above, a condenser lens 121 orthogonally arranged on a reflection optical axis O of the second mirror 120, and a digital micromirror device 122 and a digital micromirror obliquely installed. A projection lens 124 obliquely installed on the reflection optical axis O of the device 122
It will be arranged. Optical axis O of the reflected light flux of the second mirror 120
Is in the same plane as the emission optical axis O of the light valve 112.

[0007]

The projection apparatus equipped with the above-mentioned digital micromirror device is required to further sharpen the projected image, reduce the size, and save power.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned demands for a projection apparatus optical system of the prior art, and the projected image is clearer, smaller in size, power saving, and efficient in cooling. It is an object of the present invention to provide a projection device and an optical system that can be used for a long period of time.

[0009]

A first invention of the present application has a light source, a color wheel and a light pipe for passing a light beam emitted from the light source, and a concave reflection surface for reflecting the light beam passing through the light pipe. A first mirror, a second mirror arranged near the focus position of the reflected light flux of the first mirror, a digital micromirror device for receiving the reflected light flux of the second mirror, and a digital micromirror device of the digital micromirror device. A projection lens through which the reflected light flux passes, the light pipe is disposed between the reflected light flux of the second mirror and the reflected light flux of the digital micromirror device, and between the first mirror and the second mirror. The optical system of the projection device is characterized in that a light blocking member with a circular aperture is arranged on the optical axis of.

According to a second aspect of the present invention, a housing has a light source, a color wheel and a light pipe for passing a light beam emitted from the light source, and a concave reflection surface for reflecting the light beam passing through the light pipe. A first mirror, a second mirror arranged near the focus position of the reflected light flux of the first mirror, a digital micromirror device for receiving the reflected light flux of the second mirror, and a digital micromirror device of the digital micromirror device. A projection lens through which the reflected light flux passes, the light pipe is disposed between the reflected light flux of the second mirror and the reflected light flux of the digital micromirror device, and between the first mirror and the second mirror. In the projection device, a light blocking member with a circular aperture is arranged on the optical axis of.

In an embodiment of the present invention, the first mirror is
It is characterized by being a spherical or aspherical concave front surface mirror or a concave rear surface mirror. The second mirror is a spherical surface or a plane mirror. The first mirror and the second mirror have an oxidation protection film formed on a silver layer. The support member of the light pipe has an opening through which the reflected light flux of the digital micromirror device passes.

[0012]

Embodiments of the projection apparatus of the present invention are as follows. In a housing (not shown), a light valve 12 with a reflector 10, a color wheel 14 and a light pipe 16 orthogonally arranged on a projection optical axis O of the reflector 10, and a first mirror 18 which is a concave mirror obliquely installed. A light shield plate 19 with a circular aperture arranged orthogonally on the reflection optical axis O of the first mirror 18, a second mirror 20 of a flat surface mirror obliquely installed, and a reflection optical axis O of the second mirror 20.
A condenser lens 21 and an obliquely arranged digital micromirror device 22, and a projection lens 24 obliquely arranged on the reflection optical axis O of the digital micromirror device 22 are arranged above. Second mirror 2
The optical axis O of the reflected light flux of 0 is located below the light valve 12, and the reflected optical axis O of the digital micromirror device 22 is located above the light valve 12.

The reflector 10 is an elliptical mirror, and one focal point is at or near the arc gap 13 of the light valve 12. The reflecting surface of the reflector 10 is a cold mirror provided with a dielectric multi-layer coating that transmits not only visible light, but more specifically the infrared region having a wavelength longer than 700 nm. In the color wheel 14, a band-pass filter that splits a light flux into R (red) G (green) B (blue) is divided into segments and passes through. The RGB light is switched and transmitted in the order determined by the time difference.

In order to increase the total amount of light projected by the projection device, a part of the segment of the color wheel 14 is RG.
It may be a colorless transparent part instead of B. The necessity of providing the colorless and transparent portion is mainly determined by the commercial properties of the projection device such as a projector, that is, the specifications such as color reproducibility, light amount, and contrast ratio. The motor 30 that drives the color wheel 14 is an outer rotor type motor for preventing shaft shake.

The light pipe 16 for receiving the light flux passing through the color wheel 14 and averaging the light flux in the light flux cross section is a solid glass rod pipe or a light tunnel having a hollow interior with a reflective coating. In the solid glass rod pipe, total reflection can be secured by making the incident angle larger than the critical angle.
Further, the glass rod pipe has an advantage that the outer surface serves as a reflecting surface and therefore has a volume smaller than that of the light tunnel, but the outer surface must be exposed to the air, and the outer surface is damaged. There is an annoyance that it should not happen.

The reflective coating on the inner surface of the light pipe 16 is aluminum vapor deposition, preferably silver vapor deposition. When the light tunnel is adhered and stopped, the temperature inside the projection device is often high, and attention must be paid to the selection of the adhesive.
The light emitting portion of the light valve 12, that is, the arc gap 13
Has a predetermined length, the light pipe 16
Even at the focal point of the reflector 10 in the vicinity of the incident surface of, the light is not focused on a point. Therefore, in order to minimize the light amount loss due to the incidence from the light valve 12 to the light pipe 16, it is desirable that the incident surface of the light pipe 16 be large enough to cover the diffused light flux like a surface light source.

The light rays forming the light beam incident on the light pipe 16 are transmitted while being repeatedly reflected in the light pipe 16 and are averaged on the emission surface.
The length in the optical axis direction is required to ensure a predetermined number of reflections. That is, if the light pipe 16 is too short, sufficient averaging cannot be performed, while if it is too long, the light amount loss becomes large, which is not preferable.

In order to reduce the diameter of the second mirror 20, the radius of curvature of the first mirror 18 is determined to be small so that the light beam is focused on the second mirror 20. As a result, the light flux reflected by the second mirror 20 causes a large aberration and becomes non-uniform on the digital micromirror device 22, so that the condenser lens 21 is made an aspherical lens to remove the aberration and the digital Micromirror device 2
The received light of 2 is made uniform.

The tilt angles of the normal vector 53 of the first mirror 18 and the normal vector 54 of the second mirror 20 in the three-dimensional space are determined as follows with reference to FIGS. 1 to 5. Angles α81 and β8 formed by the normal vector 53 of the first mirror between the XY plane, the XZ plane, and the YZ plane xy
1, γ81 is expressed by the following equation.

[0020] Here, p and r are parameters. The positive direction of the X axis is rightward with respect to the paper surface of FIG.
The positive directions of the Y axis and the Z axis are rightward and upward, respectively, with respect to the paper surface of FIG. θ: The angle formed by the optical axis of the incident light, which passes through the centers of the light valve and the reflector and is incident on the first mirror, with the XY plane in the XZ plane. α ₈₁ , β ₈₁ , γ ₈₁ : Angles formed by the normal vector 53 of the first mirror from the XZ plane, the XY plane, and the XY plane in the XY plane, the XZ plane, and the YZ plane (FIGS.
5). A and B: Angles formed by the optical axes 56 of the reflected light reflected from the first mirror from the XZ plane and the XY plane in the XY plane and the XZ plane, respectively (see FIGS. 1 and 2).

The angles α ₈₂ , β ₈₂ and γ ₈₂ formed by the normal vector 54 of the second mirror are expressed by the following equations. Here, n and p are parameters. α ₈₂ , β ₈₂ , γ ₈₂ : The normal vector 54 of the second mirror is the XY plane, the XZ plane, the XZ plane in the YZ plane,
XY plane, an angle formed from the XY plane (see FIGS. 1, 2, and 5). C, D: Incident light 57 on the DMD reflected from the second mirror
Are angles formed by the YZ plane and the XY plane in the XZ plane and the YZ plane, respectively (see FIGS. 3 and 5).

Next, the first mirror 18 in the three-dimensional space
An example of calculation of the tilt angles of the normal vector 53 and the normal vector 54 of the second mirror 20 is shown. (Inclination angle of the normal vector of the first mirror) θ = −10 °, A = 12 °, B = 15 ° The angles α ₈₁ , β ₈₁ , formed by the normal vector 53 of the first mirror
Find γ ₈₁ . = 0.9461890 = 0.9848078 = 5.9460758 ° = 10.983390 ° = 64.788624 °

(Inclination angle of the normal vector of the second mirror) θ = 10 °, A = 12 °, B = 15 °, C = -10 °,
D = 30 ° Angles α ₈₂ , β ₈₂ formed by the normal vector 54 of the mirror M2,
Find γ ₈₂ . = 0.9461890 = 0.85610146 = -126.95028 ° (-180 ° <α ₈₂ ≤ 0) = -136.76076 ° (-180 ° <β ₈₂ ≤ 0) = -144.72718 ° (-180 ° <γ ₈₂ ≤ 0)

As shown in FIG. 6, the light shield plate 19 has a circular aperture 60, and its surface is coated with a non-reflective black coating. The light pipe 1 is provided around the light-shielding plate 19.
A notch 62 having an opening angle of about 90 degrees with which 6 is engaged is provided. As shown in FIG. 7, the light pipe 16 having the entrance surface and the exit surface parallel to each other and having a square shape has (a) all four surfaces except the entrance surface and the exit surface covered with the light shielding member 64, and (b) the entrance surface. The three surfaces out of all the four surfaces except the surface and the exit surface are covered with the light blocking member 64, and (c) all the four surfaces except the entrance surface and the exit surface are covered with the light blocking member 64, etc. Therefore, it is desirable to block the light leaking from the light pipe 16.

The light pipe support member 68 for supporting the light pipe 16 is attached to a housing (not shown) near the digital micromirror device 22 as shown in FIG. An opening 70 through which the reflected light flux of the device 22 passes is provided.

[0026]

According to the projection apparatus optical system and the projection apparatus of the present invention, it is possible to provide a projection apparatus which is smaller in size, saves power, and efficiently cools and can be used continuously for a long time.

[Brief description of drawings]

FIG. 1 is a front view of an optical system of a projection device according to an embodiment of the present invention.

FIG. 2 is a plan view of the projection device optical system of the embodiment of the present invention shown in FIG.

FIG. 3 is a right side view of the projection apparatus optical system of the embodiment of the present invention shown in FIG.

4 is an enlarged view of a portion related to a first mirror and a second mirror in the right side view of FIG. 3, in which a normal vector of the first mirror is entered.

5 is an enlarged view of a portion relating to the first mirror and the second mirror in the right side view of FIG. 3, in which the normal vector of the second mirror is entered.

FIG. 6 is a front view of the light shielding plate of the embodiment.

FIG. 7 is a perspective view of a light pipe and a light shielding member according to the embodiment.

FIG. 8 is a perspective view of a light pipe support member of the embodiment.

FIG. 9 is a front view of a projection apparatus optical system using a conventional digital micromirror device.

[Explanation of symbols]

10 reflector 12 Light valve 14 color wheel 16 light pipes 18 First mirror 19 Light shield 20 second mirror 22 Digital Micromirror Device 24 Projection lens 30 motor 53 Normal vector of the first mirror 54 Normal vector of the second mirror 60 circular aperture 64 Light-shielding member 68 Light pipe support member

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03B 21/00-21/30 G02B 27/18

Claims (6)

(57) [Claims] 1. A light source, a color wheel and a light pipe for passing a light beam emitted from the light source, a first mirror having a concave reflecting surface for reflecting the light beam passing through the light pipe, and a first mirror of the first mirror. A second mirror arranged near the focal position of the reflected light flux; a digital micromirror device for receiving the reflected light flux of the second mirror; and a projection lens through which the reflected light flux of the digital micromirror device passes. And the light pipe is arranged between the reflected light flux of the second mirror and the reflected light flux of the digital micromirror device, and the first mirror and the second mirror
An optical system for a projection device, wherein a light blocking member with a circular aperture is arranged on the optical axis between the mirrors. 2. The projection apparatus optical system according to claim 1, wherein the first mirror is a spherical or aspherical concave front surface mirror or a concave rear surface mirror. 3. The projection apparatus optical system according to claim 1, wherein the second mirror is a spherical surface or a plane mirror. 4. The first mirror and the second mirror each have an oxidation protection film formed on a silver layer.
The optical system of the projection device according to 1. 5. The optical system according to claim 1, wherein the support member of the light pipe has an opening through which the reflected light flux of the digital micromirror device passes. 6. A light source, a color wheel and a light pipe for passing a light beam emitted from the light source, a first mirror having a concave reflection surface for reflecting the light beam passing through the light pipe, and A second mirror arranged near the focusing position of the reflected light flux of the first mirror, a digital micromirror device for receiving the reflected light flux of the second mirror, and a reflected light flux of the digital micromirror device pass through. A projection lens is arranged, the light pipe is arranged between the reflected light flux of the second mirror and the reflected light flux of the digital micromirror device, and on the optical axis between the first mirror and the second mirror. A projection device in which a light shielding member with a circular aperture is arranged.